Appendix - Mammography Kvp Measurements On Hologic Selenia - Radcal Accu Series User Manual

APPENDIX -
Mammography kVp measurements on Hologic Selenia
Using a Radcal kVp Meter to Measure kVp's on Hologic Selenia Mammographic X-ray
Machine Equipped with a Tungsten-Rhodium, Silver Tube Option
A Radcal kV meter with a 40X series Mo sensor may be used with a look-up correction algorithm to
obtain Selenia W-Rh, Ag kVp's with an accuracy of +/- one kVp. Radcal recommends the Selenia
Tungsten-Ag/Rh tube be calibrated as follows.
After going into manual mode on the Hologic machine and selecting large focal spot,100mAs, place the
Radcal 40X9-Mo kV sensor on top of the Bucky table. The small compression paddle may be left
in-beam. Align the Radcal kV sensor so that its long axis is 90 degrees to the tube anode -cathode axis
so as to eliminate heel effect. Move the sensor about one inch in from the table edge. Center the sensor
right to left. Do not to forget to protect the imaging plate by placing and then smoothing out a lead apron
over it.
Use the Rhodium track to calibrate the 22 to 39 kV Selenia range and the Silver track to refine the 22 to
24 kV range to obtain a few more tenths accuracy if required from 22 to 24 kV. An example Selenia
calibration is shown below.
A Tungsten/Silver setting is different from the Tungsten/Rhodium setting. There is a range of calculated
kVp's (25-33 kV) that exceed a set error band and the instrument will show an error message as a result.
The data used to construct the correction algorithm were recorded by comparing a kVp's obtained with
Radcal Dynalyzer High Voltage Divider (True kVp) and the kVp's displayed on Radcal kVp meters during
Selenia exposures with the small compression paddle in-beam. These data were obtained from five
Selenia machines during Acceptance testing in manual mode.
Example of a Selenia calibration
Dynalyzer
Set kVp True kVp
22 22.0
23 23.0
24 24.0
25 25.0
26 26.0
27 27.0
28 28.0
29 29.0
30 30.0
31 31.0
32 32.0
33 33.0
34 34.0
35 35.0
36 36.0
37 37.0
38 38.0
39 39.0
Ag Rh
9096 kVp 9096 kVp
22.5 22.5
23.0 23.5
24.2 25.0
25.6
26.1
27.3
28.1
29.3
30.1
30.9
32.1
33.2
34.4 34.2
35.4 35.1
36.3 36.1
37.3 37.1
38.4 38.1
39.4
Ag Rh
Radcal-True Radcal-True
0.5
0.0
0.2
0.4
0.4
0.3
0.3
0.4
47
0.5
0.5
1.0
0.6
0.1
0.3
0.1
0.3
0.1
-0.1
0.1
0.2
0.2
0.1
0.1
0.1
0.1
0.4